In May 1942, Japanese Admiral Isoroku Yamamoto sought to draw the US Pacific Fleet into a battle where he could overwhelm and destroy it. To accomplish this he planned an invasion of Midway Island which would provide a base for attacking Hawaii. Using decrypted Japanese radio intercepts, Admiral Chester Nimitz was able to counter this offensive. On June 4, 1942, US aircraft flying from USS Enterprise, USS Hornet, and USS Yorktown attacked and sunk four Japanese carriers, forcing Yamamoto to withdrawal. The Battle of Midway marked the turning point of World War II in the Pacific. The Battle of Midway was predominently fought on June 4, 1942, though operations did continue until June 7. At 04:30 on June 4, Vice Admiral Chuichi Nagumo, commanding the Japanese carriers, launched 108 planes to attack Midway Island, as well as seven scout planes to locate the American fleet. Brushing aside the island's small force of fighters, the Japanese planes pounded Midway's installations. While returning to the carriers, the strike leaders recommended a second attack. In reponse, Nagumo ordered his reserve aircraft, which had been armed with torpedoes, to be rearmed with bombs. After this process had commenced, a scout plane from the cruiser Tone reported locating the American fleet. On the night of June 4th, both sides retired to plan their next move. By 02:55, Yamamoto ordered his fleet to return to base. In the following days, American aircraft sunk the cruiser Mikuma, while the Japanese submarine I-168 torpedoed and sank the disabled Yorktown. The defeat at Midway broke the back of the Japanese carrier fleet and resulted in the loss of invaluable air crews. It also marked the end of major Japanese offensive operations as the initiative passed to the Americans. That August, US Marines landed on Guadalcanal and began the long march to Tokyo.
Battle of the Coral Sea
In the wake of their stunning victories in early 1942, the Japanese sought to extend their control by taking all of New Guinea and occupying the Solomon Islands. This would eliminate the last Allied base between Japan and Australia as well as would provide a security perimeter around Japan's recent conquests in the Dutch East Indies. It was also hoped that the operation would draw the US Navy's carriers into battle so that they could be destroyed. To accomplish these missions, three Japanese fleets sortied from Rabaul in April 1942.
While one moved towards Tulagi in the Solomons, another sailed south towards the main Allied base on New Guinea, Port Moresby. These invasion forces were screened by Vice Admiral Takeo Takagi's covering force centered around the carriers Shokaku and Zuikaku and the light carrier Shoho. Arriving at Tulagi on May 3, Japanese forces quickly occupied the island and set up a seaplane base. Alerted to Japanese intentions by radio intercepts, Admiral Chester Nimitz, Commander-in-Chief of the US Pacific Fleet, dispatched the carriers USS Yorktown and USS Lexington to the Coral Sea to protect Port Moresby.
Led by Rear Admiral Frank J. Fletcher, Yorktown raced to the area and launched three strikes against Tulagi on May 4, 1942. Hitting the island hard, they badly damaged the seaplane base and eliminated its reconnaissance capabilities for the coming battle. In addition, Yorktown's aircraft sank a destroyer and five merchant ships. Steaming south, Yorktown joined Lexington later that day. Two day later, land-based B-17s from Australia spotted and attacked the Port Moresby invasion fleet. Bombing from high-altitude, they failed to score any hits.
Throughout the day both carrier groups searched for each other with no luck as cloudy skies limited visibility. With night setting in, Fletcher made the difficult decision to detach his main surface force of three cruisers and their escorts. Designated Task Force 44, under the command of Rear Admiral John Crace, Fletcher ordered them to block the probable course of the Port Moresby invasion